The pressure of hydraulic or pneumatic systems is controlled by valves that control the pressure by a modulating movement between at least two axial forces acting against one another. The axial forces result from at least one pressure and a further external force which, for example, are applied by a spring, a solenoid or a second hydraulic pressure to the valve gate.
The constantly increasing demands on the quality and speed of control of hydraulic or pneumatic control systems result in systems that are more and more vulnerable to disturbances. This is due, for example, to the compromise that is required to achieve a high control speed of the valves, because ever smaller valve gates are used which, however, are very vulnerable to disturbances of all sorts (disturbance force/return surface=pressure disturbance) because of their small return surface (gate surface on which the pressure to be modulated is applied). This is particularly the case when the control forces for actuating the valve gate are very small and/or high control pressures have to be reached.
In hydraulic systems which are exposed to acceleration, like motor vehicle transmissions, the force ratios at the valve gates, among others, are influenced by the mass forces resulting from the acceleration. This effect is especially pronounced if the valve gates are arranged with their longitudinal axis, and thus their only translational degree of freedom, in the direction of travel. As a result, the pressure ratios also undesirably change in the hydraulic system. In particular, in electromagnetic pressure controllers designated as a pressure pilot valve, and thus in the pilot-actuated valve gates for controlling the pressure in the start-up clutch, the required values of the pressure to be controlled cannot precisely be maintained in the acceleration phase owing to this disturbance, as a result of which the transmission capacity and performance of the clutch are impaired. This problem is similar in pneumatic systems.
A possible measure to prevent the influence of the longitudinal acceleration is the arrangement of the valve gates which are used for controlling the start-up clutch, as well as possibly available pressure pilot valves with their longitudinal axis perpendicular to the direction of travel. The mass forces resulting from the longitudinal acceleration hereby actuate perpendicularly to the only translational degree of freedom of the valve gate and thus have no influence on the pressure ratios at the valve gates. This perpendicular arrangement of the valve gate is, however, disadvantageous in vehicles that have a drive motor with a crankshaft oriented in the longitudinal direction of the vehicle because the rotational irregularities of the drive motor actuate tangentially to the crankshaft axis, and consequently likewise to the direction of travel, thus influencing the force ratios at the valve gates due to the resultant mass forces. Because of the high motor arrangements and very high accelerations, this in turn affects the pressure settings and may further result in wear and/or destruction of the valve system.
Another known device for solving the problem is an angular pressure regulator. In this case, only the pressure controller which is, for example, configured as an electromagnetic proportional valve, is arranged with its longitudinal axis at an angle of 90° to the longitudinal axis of the valve gate of the pressure control valve, whereby the acceleration of the whole system only acts on the valve gate and the pilot pressure remains unaffected. Here, the disadvantages are the complex production or conditioning and consequent costs, as well as the requirement for a larger installation space.